1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a wireless network, and more particularly, to a method and apparatus for keeping information in routing tables consistent throughout a wireless network.
2. Description of the Related Art
With the spread of Internet networks and the great increase in the amount of multimedia data transmitted via networks, the demand for high-speed communication networks has steadily increased. Regarding high-speed communication networks, a local area network (LAN) was developed in the late 1980s to have a transmission speed of 1-4 Mbps. A 100 Mbps Ethernet which is implemented based on a recent LAN standard is widely used. Recently, research has been vigorously conducted to develop a gigabit Ethernet. Various attempts to wirelessly access a network and carry out wireless network communication have expedited the research and development of wireless local area networks (WLAN), and thus, WLANs are now widespread. A WLAN provides lower data transmission rates and lower stability than a wired LAN. However, it is more convenient to establish a WLAN than to establish a wired LAN because a WLAN does not need wires, and a WLAN offers higher mobility than a wired LAN. Therefore, the demand for WLANs has steadily increased.
With the growing demand for increasing the amount of data transmitted over networks and recent developments in wireless data transmission technology, various improved versions of the IEEE 802.11 standard, such as the IEEE 802.11a, 802.11b, 802.11g, 802.11n, and 802.11s standards, have already been ratified or are expected to be ratified in the near future through standardization processes.
A device called an access point is used in a WLAN environment to provide LAN services to a wireless terminal. An access point performs almost the same functions as a hub in a wired LAN environment. The IEEE 802.11s standard defines a WLAN mesh, which is a LAN constituted by a plurality of access points, and enables the access points to wirelessly communicate with one another.
FIG. 1A is a diagram of a related wired LAN environment in which a plurality of access points are connected with one another by wires, and FIG. 1B is a diagram of a WLAN mesh environment which is established by a plurality of access points according to the 802.11s standard. In both the related wired LAN environment and the WLAN mesh environment, stations are wirelessly connected to an access point. However, in the related wired LAN environment of FIG. 1A, a plurality of access points AP1 through AP4 are connected to one another in a wired manner. Thus, routing information specifying which of the access points AP1 through AP4 each station is associated with is transmitted via wire. Therefore, the routing information is unlikely to be lost while being transmitted.
On the other hand, in the WLAN mesh environment of FIG. 1B, a plurality of access points AP1 through AP4 wirelessly communicate with one another. Each of the access points AP1 through AP4 transmits, via a wireless medium, information about a plurality of stations associated with the corresponding access point. For example, the access point AP1 may transmit its routing information to the access points AP2 and AP3, and the access point AP3 may transmit the routing information of the access point AP1 to the access point AP4. This type of data transmission among a plurality of access points is referred to as a multi-hop method. In the multi-hop method, if an intermediate access point between a sending access point and a receiving access point does not function correctly, it may not be able to receive data from the sending access point. For example, if the access point AP3 fails to receive the routing information of the access point AP1 due to instability of the wireless medium, the access point AP4 also may not be able to receive the routing information of the access point AP1. Therefore, it is more difficult to share a routing table in the WLAN mesh environment of FIG. 1B than in the wired LAN environment of FIG. 1A.
In short, a WLAN mesh environment is the same as a typical wireless network environment in that a plurality of wireless terminals are within the communication range of an access point and are thus controlled by the access point. However, in the WLAN mesh environment, unlike in the typical wired network environment, a plurality of access points wirelessly communicate with one another in a multi-hop manner. In order for a plurality of access points to wirelessly communicate with one another in a multi-hop manner, a wireless mesh routing protocol must be executed on Layer 2, i.e., on a link layer, and data paths to wireless terminals where the wireless mesh routing protocol cannot be executed must be secured while satisfying all the requirements prescribed in the IEEE 802.11 standard. Therefore, it is necessary to effectively transmit information about wireless terminals not having the wireless mesh routing protocol, i.e., legacy stations, over a network established between access points in a multi-hop method and to efficiently maintain the consistency of all station information stored in the access points. In particular, given that a wireless network environment is generally unstable and broadcast techniques used for distributing information over a wireless network are yet to be sufficiently reliable, some access points are highly likely to fail to receive information transmitted thereto. Therefore, it is necessary to develop a mechanism for detecting data loss during transmission of data between access points in a wireless network environment and updating data that is believed to be lost.